Hot Topics:

CU-Boulder: Ancient human relative had diet similar to chimps

Finding sets Australopithecus sediba apart from other hominids

By Laura Snider Camera Staff Writer

Posted:
06/30/2012 11:41:58 AM MDT

Updated:
06/30/2012 11:42:11 AM MDT

Distinguishing itself from virtually all other hominids that have so far been studied, an ancient human relative that roamed South Africa about 2 million years ago may have preferred a chimpanzee-like diet of fruits, bushes and even bark, according to new research involving scientists at the University of Colorado.

Other human ancestors appear to have had a diet more similar to a cow than a chimpanzee, preferring to graze on grasses and sedges than eat harder foods.

CU doctoral student Paul Sandberg and his adviser, CU anthropologist Matt Sponheimer, used lasers to free carbon gases from the teeth of Australopithecus sediba, a species of hominid discovered just a few years ago at the Malapa site in South Africa. The species, of which only two individuals have been formally identified, is particularly fascinating to anthropologists because it has physical characteristics that are both primitive, such as ape-like arms, and modern, such as human-shaped hips.

"They have this really unique mix of traits," Sandberg said.

Some scientist believe that the new species may be a bridge between the Homo genus, which includes humans, and the Australopithecus genus, made up of earlier primates that walked upright on two legs.

Sandberg and Sponheimer, both co-authors of the paper appearing in the journal Nature, have now discovered that sediba may be unique in another way -- what it ate -- as well.

Plants typically grow using one of two major photosynthetic processes, known as C3 or C4, and scientists can distinguish between the carbon created through the two processes. Plants using the C4 process include grasses and sedges, while tougher plants, such as trees, shrubs and bushes, use the C3 process. As animals eat plant matter, the telltale carbon is also absorbed into their tooth enamel.

Advertisement

Sandberg and Sponheimer measured the carbon gas released from the tooth enamel of sediba by lasers to determine that the species -- or at least those two individuals -- overwhelmingly preferred to eat C3 plants, even when C4 plants were available.

By contrast, testing of the other 81 samples of tooth enamel collected from a range of species of early human ancestors done in the last decade or so shows that they all preferred dining on C4 plants.

"The carbon isotope composition (of sediba) is similar to chimpanzees," Sandberg said. "Faced with a situation where you have C3 foods and C4 foods, the chimpanzee chews C3 foods. All these other hominids, when faced with a similar choice, are going to go out in the grassland and actually eat (C4 foods)."

The technique used by the CU scientists was first published in a scientific journal in 1994, and Sponheimer began using the method soon after. For some time, the technique -- which destroys a small part of the tooth -- was not permitted to be used on east African fossils, so most of the work was done on hominids found in South Africa, Sponheimer said.

"In east Africa the reigning idea was that these fossils were too precious to be subject to minimally destructive analysis for almost any reason," Sponheimer wrote in an e-mail.

But over the years, the technique has become even less destructive, and east African collections have been opened to testing, and within the next year, all major hominid species will have been analyzed, Sponheimer said.

Sandberg said that the next step for the current study -- which was led by the Max Planck Institute of Evolutionary Anthropology in Leipzig, Germany, and worked on by other scientists from around the United States -- is to test the teeth of more sediba individuals to see if the results are the same.

"A sample of two is not big," he said. "There are going to be more samples out of Malapa, and we hope to (test them)."Contact Camera Staff Writer Laura Snider at 303-473-1327 or sniderl@dailycamera.com.

Dye pours in 19 for TrojansSmothering. Confounding. And just a tad frustrating ... at least for the opposition.
Longmont's defense, whether they are playing a 1-3-1 zone, 2-3 zone or man-to-man -- and it can switch from possession to possession -- can give teams fits. Full Story

The Boulder alt-country band gives its EPs names such as Death and Resurrection, and its songs bear the mark of hard truths and sin. But the punk energy behind the playing, and the sense that it's all in good fun, make it OK to dance to a song like "Death." Full Story